206 MULTIPLE ALLELOMORPHS 
and yellow), and yellow form a triple system. 
Emerson’s case for pod and leaves in beans—green 
pods, green leaves; yellow pods, yellow leaves; 
yellow pods, green leaves—also fulfill the conditions 
of a triple allelomorph system. Shull has reported a 
case in Lychnis which he interprets as due to triple 
allelomorphs for sex-determining factors. Two of 
them give reversible mutations as have white and 
eosin in Drosophila. 
Cases in which more than three allelomorphs have 
been found may next be considered. The cases seem 
to show that here also the same character is affected 
by each of the mutant factors that form the multiple 
system. In a few instances the characters have been 
recognized as due to multiple allelomorphs, but in 
most of them no sufficient interpretation has been 
offered or else the explanation of complete linkage 
has been advanced. 
Tanaka has reported a case in the silkworm moth 
which seems best interpreted as one of quadruple 
allelomorphs. The four larval patterns called striped, 
moricaud, normal, and plain (Fig. 51), are the char- 
acters involved. Besides showing the ordinary be- 
havior of multiple allelomorphs when mated together 
these characters show linkage to another pair of 
factors (for yellow and white cocoon color). So far 
as the data go, the strength of this linkage seems to 
be the same in all combinations tested. 
In mice it has been shown (Cuénot, Morgan, 
Sturtevant, and Little) that yellow, black, gray with 
gray belly (wild type), and gray with white belly 
